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Limewater is a saturated solution of Ca(OH)2 in water. It is used to test for the presence of CO2 in a gaseous mixture. Write an equation for the reaction between limewater and CO2. A saturated solution of Ba(OH)2 can be used instead of Ca(OH)2 to test for CO2. A saturated solution of Mg(OH)2 cannot be used for this test. Explain why a saturated solution of Ba(OH)2 can be used to test for CO2. Explain why a saturated solution of Mg(OH)2 cannot be used to test for CO2. Describe and explain the trend in the thermal stabilities of the carbonates down Group 2. Nickel carbonate, NiCO3, decomposes on heating. Use the Data Booklet to explain whether NiCO3 will decompose more or less readily than CaCO3.

9. The Periodic Table: chemical periodicity  →  9.2. Periodicity of chemical properties of the elements in Period 3

10. Group 2  →  10.1. Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds

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Complete the following electronic configurations. • the cobalt atom, Co 1s22s22p6 • the cobalt(ion, Co2+ 1s22s22p6 State the colours you would observe when concentrated HCl is added to an aqueous solution of cobalt(nitrate, Co(NO3)2. Give the formulae and geometry of the complexes formed. There are two isomers with the formula Ni(R3P)2I2, but only one structure with the formula Co(R3P)2I2. (R = alkyl, R3P is a monodentate ligand) Draw diagrams showing the structure of Co(R3P)2I2 and the two isomers of Ni(R3P)2I2. Ni(R3P)2I2 Ni(R3P)2I2 Co(R3P)2I2

3. Chemical bonding  →  3.4. Covalent bonding and coordinate (dative covalent) bonding

17. Carbonyl compounds  →  17.1. Aldehydes and ketones

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One method of producing hydrogen from natural gas is the reaction between hydrogen sulfide and methane. 2H2S+ CH4CS2+ 4H2Write the expression for Kp for this reaction, and state its units. Kp = units The initial partial pressures of the two gases in a mixture at 1000 K are recorded. H2S200 atm CH4100 atm The mixture is left to reach equilibrium. It is found that the equilibrium partial pressure of CS2is 2 atm and that of the remaining CH4is 98 atm. Calculate the equilibrium partial pressures of H2Sand H2. p(H2S) = atm p(H2) = atm Calculate the value of Kp at this temperature. Kp = Predict the sign of ∆S o for this reaction. Explain your answer. 2H2S+ CH4CS2+ 4H2∆H o = +241 kJ mol–1 The free energy change, ∆G o, for this reaction at 1000 K is +51 kJ mol–1. Calculate the value of ∆S o for this reaction, stating its units. ∆S o = units How would the value of ∆G o, and hence the spontaneity of this reaction change as the temperature increases? Explain your answer.

7. Equilibria  →  7.1. Chemical equilibria: reversible reactions, dynamic equilibrium

5. Chemical energetics  →  5.1. Enthalpy change, \(\Delta H\)

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Define the term standard cell potential, . The following incomplete diagram shows the apparatus that can be used to measure the for a cell composed of the Fe3+ / Fe2+ and Ag+ / Ag half-cells. A B C D Complete the diagram, labelling the components you add. Identify the components A-D. A B C D Use E o values to write an equation for the cell reaction that takes place if the two electrodes in are connected by a wire and the circuit is completed. Another electrochemical cell was set up using 0.31 mol dm–3 Ag+instead of the standard Ag solution. Use the Nernst equation, E = E o + 0.059 log [Ag+], and the relevant E o values to calculate the new E cell in this experiment. E cell = V

2. Atoms, molecules and stoichiometry  →  2.3. Formulas

11. Group 17  →  11.3. Some reactions of the halide ions

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Dicarboxylic acids dissociate in stages. stage 1 stage 2 HO2C(CH2)nCO2H HO2C(CH2)nCO2 – + H+ –O2C(CH2)nCO2 – + 2H+ The pKa values for stage 1 and stage 2 for some dicarboxylic acids are listed below. n in HO2C(CH2)nCO2H pKa(1) for stage 1 pKa(2) for stage 2 2.83 5.69 4.16 5.61 4.31 5.41 For comparison, the pKa of ethanoic acid, CH3CO2H, is 4.76. State the mathematical relationship between pKa and the acid dissociation constant Ka. With reference to the table above, suggest why the pKa(1) values • are all smaller than the pKa of ethanoic acid, • become larger as n increases. Suggest why all the pKa(2) values in the table above are larger than the pKa of ethanoic acid. The monosodium salts of edible dicarboxylic acids are added to some foodstuffs as buffers. Explain what is meant by the term buffer solution. Write two equations to show how monosodium butanedioate, HO2CCH2CH2CO2Na, acts as a buffer.

7. Equilibria  →  7.2. Brønsted–Lowry theory of acids and bases

18. Carboxylic acids and derivatives  →  18.1. Carboxylic acids

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Nitrobenzene, C6H5NO2, can be reduced to phenylamine, C6H5NH2, in acid solution in a two step process. Balance the half-equation for this reaction to work out how many moles of electrons are needed to reduce one mole of nitrobenzene. C6H5NO2 + e– + H+ → C6H5NH2 + H2O The reducing agent normally used is granulated tin and concentrated hydrochloric acid. In the first step, the reduction of nitrobenzene to phenylammonium chloride can be represented by the equation shown. Use oxidation numbers or electrons transferred to balance this equation. You might find your answer to useful. C6H5NO2 + HCl + Sn → C6H5NH3Cl + SnCl 4 + H2O When 5.0 g of nitrobenzene was reduced in this reaction, 4.2 g of phenylammonium chloride, C6H5NH3Cl, was produced. Calculate the percentage yield. percentage yield of phenylammonium chloride = % Following the reaction in , an excess of NaOHwas added to liberate phenylamine from phenylammonium chloride. Calculate the mass of phenylamine, C6H5NH2, produced when 4.20 g of phenylammonium chloride reacts with an excess of NaOH. mass of phenylamine = g The final volume of the alkaline solution of phenylamine in was 25.0 cm3. The phenylamine was extracted by addition of 50 cm3 of dichloromethane. After the extraction, the dichloromethane layer contained 2.68 g of phenylamine. Use the data to calculate the partition coefficient, K partition, of phenylamine between dichloromethane and water. K partition = How does the basicity of phenylamine compare to that of ethylamine? Explain your answer. Phenol can be synthesised from phenylamine in two steps. NH2 OH + N2 E step 1 step 2 State the reagents and conditions for steps 1 and 2. step 1 step 2 Draw the structure of the intermediate compound E in the box above.

12. Nitrogen and sulfur  →  12.1. Nitrogen and sulfur

14. Hydrocarbons  →  14.2. Alkenes

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Use the Data Booklet to draw the structure of the tripeptide Ala-Ser-Gly showing its peptide bonds in full. Ala-Ser-Gly Calculate the relative molecular mass, Mr, of Ala-Ser-Gly. Mr = Electrophoresis can be used to separate mixtures of amino acids and peptides. A mixture of the tripeptide Ala-Ser-Gly and its three constituent amino acids was subjected to electrophoresis in a buffer at pH 11. Draw the structure of serine at pH 11. At the end of the experiment the following results were seen. mixture applied here P G H Q R S I F Identify the components labelled F-I in the above diagram. F G H I Suggest the identities of the species responsible for spot P, spot S. Explain your answers. State the reagents and conditions needed for converting the tripeptide into its three constituent amino acids. Name the type of reaction in .

22. Analytical techniques  →  22.2. Mass spectrometry

14. Hydrocarbons  →  14.2. Alkenes

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Chromyl chloride, CrO2Cl 2, can be prepared by heating a mixture of potassium dichromate(and potassium chloride with concentrated sulfuric acid. K2Cr2O7 + 4KCl + 3H2SO4 → 2CrO2Cl 2 + 3K2SO4 + 3H2O Use the following data to complete the Hess’ Law cycle and calculate the enthalpy change of the reaction, ∆Hr. compound enthalpy change of formation, / kJ mol–1 K2Cr2O7 –2061 KCl –437 H2SO4 –814 CrO2Cl 2 –580 K2SO4 –1438 H2O –286 K2Cr2O7 + 4KCl + 3H2SO4 ∆Hr 2CrO2Cl 2 + 3K2SO4 + 3H2O elements ∆Hr = kJ mol–1 There are two isomeric complex ions with the formula [Cr(NH3)4Cl 2]+. One is green and the other is violet. Suggest the type of isomerism shown by these complex ions. Explain why these two complex ions • are coloured, • have different colours.

5. Chemical energetics  →  5.1. Enthalpy change, \(\Delta H\)

11. Group 17  →  11.4. The reactions of chlorine

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The anti-inflammatory drug ketoprofen can be synthesised from benzene via the following five steps. O O Br step 1 step 5 step 2 step 3 T, (C15H14O) U step 4 O CO2H ketoprofen Suggest the structures of compounds T and U and draw them in the boxes above. Suggest reagents and conditions for steps 1-5. step 1 step 2 step 3 step 4 step 5 What types of reaction are steps 1 and 5? step 1 step 5

21. Organic synthesis  →  21.1. Organic synthesis

17. Carbonyl compounds  →  17.1. Aldehydes and ketones

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Ethanedioic acid, C2O4H2, occurs in many vegetables. The amount that occurs in spinach can be estimated as follows. • 40.0 g of spinach leaves are crushed and mixed with distilled water, using a mortar and pestle. • The mixture is filtered, and the leaves are washed with a little more water. • The combined filtrate and washings are made up to 100.0 cm3 with water. • A 25.0 cm3 portion of the resulting solution is added to a conical flask, along with an excess of dilute sulfuric acid. • The acidified solution is warmed, and then titrated with 0.0200 mol dm–3 KMnO4. The equation for the reaction between ethanedioic acid and acidified manganate(ions is shown. 2MnO4 – + 6H+ + 5C2O4H2 → 2Mn2+ + 10CO2 + 8H2O In the titration, 15.20 cm3 of KMnO4 was required to reach the end-point. Calculate the percentage by mass of ethanedioic acid in the spinach leaves. percentage of ethanedioic acid = % Ethanedioic acid can be converted into ethanedioyl chloride: HO2CCO2H → Cl OCCOCl State a suitable reagent for this reaction. For the reactions of ethanedioyl chloride below, suggest the structures of compounds J and K and draw them in the boxes. CH3OH H2NCH2CH2NH2 K (C4H6N2O2) J (C4H6O4) COCl COCl When ethanedioyl chloride is reacted with silver ethanedioate, AgO2CCO2Ag, in ethoxyethane at –30 °C, an oxide of carbon, L, is formed. The molecule of L has no overall dipole and has molecular formula C4O6. The carbon-13 NMR spectrum of a solution of L in ethoxyethane, CH3CH2OCH2CH3, is shown below. δ Use the Data Booklet to state in the boxes below the δ values for the peaks in the spectrum which are due to the carbon atoms in ethoxyethane. CH3 CH3 CH2 CH2 O δ values Explain what the rest of the carbon-13 NMR spectrum indicates about the structure of L. When pure L is reacted with an excess of CH3OH, a mixture of three compounds is formed. L and CH3OH → M and N and O (C4O6) (C2H2O4) (C3H4O4) (C4H6O4) M is formed as one of the products when either N or O is heated with aqueous acid. The table gives information of the peaks recorded in the carbon-13 NMR spectra of M, N and O. compound peaks recorded in carbon-13 NMR spectrum M δ 162 N δ 53 δ 160 δ 162 O δ 53 δ 160 Suggest the structures of M, N and O. M, (C2H2O4) N, (C3H4O4) O, (C4H6O4) Suggest a structure for L that fits all the data given in and . L, (C4O6)

18. Carboxylic acids and derivatives  →  18.1. Carboxylic acids

11. Group 17  →  11.3. Some reactions of the halide ions

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